Why this matters
Asthma affects 8.6% of U.S. children and costs ~$56B annually. If a simple, safe prenatal nutrition step can lower risk, that’s a big win for families and public health.
The study at a glance
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Design: Single-center, double-blind, randomized, placebo-controlled trial (the gold standard).
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Who: 736 generally healthy pregnant women in Denmark, enrolled at 22–26 weeks’ gestation.
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Intervention: From week 24 until one week postpartum, participants received 2,400 mg/day EPA+DHA (≈55% EPA, 37% DHA) or olive oil placebo.
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Follow-up: Pediatricians, blinded to group assignment, tracked respiratory outcomes to age 5.
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Primary endpoint: “Persistent wheeze” ≤3 years and “asthma” >3 years (combined here as “asthma”), using a validated algorithm.
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Funding: Danish government; no donated product.
Did omega-3s raise mom’s levels?
Yes—despite active transfer of omega-3s to the fetus:
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Whole blood EPA+DHA rose from 4.9% → 6.1% in the supplement group and fell to 3.7% in placebo.
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Estimated Omega-3 Index (RBC) moved from ~6.9% → 8.3% (supplement) vs ~6.9% → 5.5% (placebo).
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Note: Danish baseline intake (~321 mg/day EPA+DHA) is higher than the U.S. (~90 mg/day), explaining the relatively high starting levels.
Main outcome: lower asthma risk—especially when mom starts low
Among 695 children with outcome data, ~20% (n=136) developed asthma by age 5.
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Overall: 17% in the omega-3 group vs 24% in placebo — a 31% relative risk reduction.
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Biggest benefit: Moms with low baseline EPA+DHA (<4.3% in whole blood; ≈Omega-3 Index <6.2%) saw a 54% reduction in their child’s asthma risk.
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Still helpful up to midrange: Protective effects extended to baseline EPA+DHA ~5.0–5.5% (≈Omega-3 Index 7.0–7.6%).
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Implication for the U.S.: With an average Omega-3 Index around ~4%, the population-level impact here could be even larger.
What about breast milk levels?
EPA+DHA in breast milk at 1 month postpartum did not predict asthma overall, with a trend only in the control group. Likely reasons:
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Supplementation stopped one week after delivery, so milk levels likely normalized by the 1-month draw.
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Milk fatty acids equilibrate in ~2 weeks, whereas RBC levels take 3–4 months, making maternal blood a steadier exposure marker.
Practical takeaways
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Screen & personalize: Testing maternal omega-3 status (e.g., Omega-3 Index) during pregnancy helps identify who stands to benefit most.
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Dose matters: Achieving/maintaining an Omega-3 Index of ~8–12% in late pregnancy aligned with lower childhood asthma risk in this trial.
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Start where intake is low: Populations with low dietary EPA+DHA may see the greatest preventive impact.
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Safety & access: EPA+DHA supplementation in pregnancy is generally well-tolerated, affordable, and supported by professional groups for multiple maternal-fetal benefits. Always discuss with your obstetric provider.
Bottom line
Third-trimester EPA+DHA supplementation reduced early childhood asthma risk, most notably when mothers began pregnancy with low omega-3 status. Measuring and optimizing maternal EPA+DHA during pregnancy is a practical, evidence-based strategy to support respiratory health in children.
